Hypericin is a natural compound found in stems and petals of plants of the genus Hypericum. Within this genus are eight families and 43 species, including the common St. John's wort plant, Hypericum perforatum. Hypericin is the principle phototoxic agent in St. John's wort. The chemical name is 1,3,4,6,8,13-hexahydroxy-10,11-dimethylphenanthro[1,10,9,8-opqra]perylene-7,14-dione (other names: 4,5,7,4′,5′,7′ hexahydroxy-2,2′-dimethyl-meso naphthodianthrone; Phenanthro[1,10,9,8-opqra]perylene-7,14-dione, 1,3,4,6,8,13-hexahydroxy-10,11-dimethyl-), a compound composed of eight conjugated rings containing six hydroxyl groups, two carbonyl and two methyl groups in a symmetric pattern when inverted about a central axis.
Hypericin is one of the most important phenanthoperylene quinones extracted mainly from plants of the genus Hypericum. Widespread attention to the antiviral and anti-tumor properties of hypericin has spurred investigations of the chemical synthesis and biosynthesis of this unique compound. However, the synthetic strategies are challenging for organic and biological chemists.
In the past, isolation of hypericin from plants was not practical on a large scale because it requires a lengthy procedure involving extraction with large columns of solvents and cumbersome chromatographic separations on silica gel columns. The main difficulty in obtaining hypericin in a pure state from the plant material resides in its separation from the accompanying pseudohypericin. This necessitates the aforementioned chromatography with the elution of a large number of fractions, only a few of which contain the pure desired material. The concentration of hypericin in the plants is very low, not more than 0.3% based on the dry plant material.
U.S. Pat. No. 8,629,302 B2 issued to Tobia et al discloses a method for making hypericin comprising steps starting from emodine to emodine anthrone which is then dimerized to protohypericin salt and then photoconverted to hypericin. However, the method requires re-circulation of protohypericin solution to effectively convert to hypericin making the process unscalable. Furthermore, the purified hypericin was hygroscopic, adsorbing moisture over storage time and found to be in a mixture of salt and acid form. Presently, there is a need for novel and highly effective systems and methods for producing synthetic hypericin having a well-defined compositional matter on a large scale.